The embodiments described herein relate to a magnetic resonance imaging apparatus having an RF coil.
An RF coil for sending transmission pulses is installed within a magnetic resonance imaging apparatus. The diameter of the RF coil is related to the size of a bore into which a subject is carried. Therefore, the value of the RF coil diameter is very important. The bore can be made large by making the RF coil diameter large, thus making it possible to diminish the sense of oppression of a subject when carried into the bore. However, if the RF coil diameter is made large, it is required to increase the electric power to be supplied to the RF coil, thus giving rise to the problem that electric power consumption increases. Moreover, since an RF shield is disposed around the RF coil, if the RF coil diameter is made large, the spacing between the RF coil and the RF shield becomes narrower. The RF shield acts to cancel a magnetic field generated by the RF coil, and the narrower the spacing between the RF coil and the RF shield, the more remarkable the action of the RF shield. Thus, there arises the problem that the narrower the spacing between the RF coil and the RF shield, the larger the electric power to be supplied to the RF coil, resulting in a further increase of electric power consumption.
The use of an elliptic RF coil has been proposed as a method for solving the above problem in, for example, Japanese Unexamined Patent Publication No. Hei 7 (1995)-222729.
However, since the RF coil described in Japanese Unexamined Patent Publication No. Hei 7 (1995)-222729 is elliptic, the coil diameter in the minor axis direction of the ellipse cannot be made large. Accordingly, there is the problem that the bore cannot be made large in the minor axis direction of the ellipse and that therefore a subject who has been carried into the bore is apt to have a sense of oppression.